The present invention relates to nuclear magnetic resonance (NMR) angiographic methods for imaging fluid flow in a sample and, more particularly, to novel NMR angiographic methods in which a single response is generated for each excitation of the sample and with many excitations occurring in each cardiac cycle, to provide medically-significant anatomy images of averaged fluid flow, in non-invasive manner.
It is known to provide NMR angiographic projection images, indicating the flow of bodily fluids through various bodily passages, for medical diagnostic purposes. Methods for producing such images are described and claimed in co-pending U.S. patent application Ser. No. 835,683, filed Mar. 3, 1986, now U.S. Pat. No. 4,714,081, issued Dec. 22, 1987, and application Ser. No. 013,592, filed Feb. 11, 1987, both assigned to the assignee of the present application and incorporated here in their entireties by reference. While those methods provide true projection images (through the entire anatomical thickness) and allow high quality NMR angiograms of arterial and venational structures to be obtained along one or more selected projection axes and with a selected direction of flow sensitivity in a sample, it is still highly desirable to obtain the same, or more, information in the NMR angiograms in a shorter time interval. This is especially important in human diagnostic imaging, where the likelihood of patient movement increases with increased imaging time. Other benefits, such as the ability to acquire three-dimensional flow information, saturate non-moving spins (for additional suppression of non-moving spins), and/or measurement of total vessel flow (particularly in a sample having a cardiac cycle) are also desirable. Accordingly, methods for providing NMR angiograms with improved features, while substantially reducing both data acquisition time and sample motional sensitivity, are highly desirable.